hi,
The color picker module parameters have been removed in the VM3 version. Instead, we have used "CSS" for stylization.
Simply because using CSS for stylization is more professional way, using module parameters for style, requires us to use "Inline CSS" which is a very very bad thing in terms of page loading, clean coding and W3C standards..
You should use "Developer Tools of Chrome (F12)" of "Firebug for Firefox" for the CSS changes and make your aesthetic changes (changing text color, background color etc..) by adding CSS rules to CSS file of the dropdown shopping cart module. If you don't know how to use "Developer Tools", then you should start using it immediately. It is a very useful tools and it will save you hours.
See this topic below for more info about how to use:
www.flexiblewebdesign.com/forum-virtuemart-2-template-puremart-support/342-using-firebug-for-customization-or-troubleshooting
Regards